Maynilad has the responsibility to operate, maintain and invest in the water and sewerage system of the 17 cities and municipalities that comprise the West Zone. These areas include: Caloocan, Las Piñas, Malabon, Manila, Muntinlupa, Navotas, Pasay, Parañaque, Valenzuela, parts of Quezon City, a part of Makati; and the cities of Bacoor, Cavite and Imus and the municipalities of Kawit, Noveleta, and Rosario in the province of Cavite.

The West Zone covers a total of 540.43 square kilometers. To manage the delivery of water and wastewater services in its coverage area, Maynilad divided the West Zone into Four District Areas composed of 12 Business Areas (BA) that are further broken down into zones, sub-zones and District Metering Areas (DMAs).